FR3073277A1 - ANTI-DEPOT WALL HEAT EXCHANGER SYSTEM - Google Patents

Abstract

A heat exchanger system comprising a wall (22) separating a first fluid from a second fluid and allowing heat exchange between said fluids. A protective film (26) of polymeric material is disposed on said wall at least on the side of the first fluid, the protective film having a front face (26.2) in contact with the first fluid and a rear face (26.1) opposite, facing the wall (22). Gas distribution means (28) are provided for dispensing a gaseous cleaning agent on the back side (26.1) side of the protective film. The protective film (26) is dense, impermeable or poorly permeable to the first fluid, while being permeable to said gaseous cleaning agent, so as to allow the gaseous cleaning agent to pass through the protective film towards the front face (26.2) of the -this.

Description

Description

The present invention generally relates to the field of heat exchangers and relates more particularly to the problem of fouling of these surfaces.

Many processes based on heat exchange use a solid material, the main function of which is to provide energy transfer. Metals are typically used for heat exchangers. Depending on the applications, the heat exchangers have simple or complex shapes, but are typically constructed so as to be able to allow the transfer of a heat flow from a hot fluid to a cold fluid through a wall without direct contact between the two fluids (without mixing them).

For low level thermal energy recovery applications (heat at temperature levels typically between 60 and 120 ° C), which currently constitute a major issue (both in the industrial and domestic fields), the use dense polymer materials has many advantages: efficiency, compactness, lightness, low cost (both from the point of view of the constituent materials and of the production technologies).

A particularly increased problem in exchangers is that of fouling, scaling or clogging of surfaces with biofilms or inorganic deposits. These various phenomena cause a drop, often significant, in the performance of the devices (fall in heat flux) and constitute a major challenge.

The solutions used today consist mainly of injecting a cleaning agent, for example chlorine for biofilms, into the fluid circulating in a pipe or along a surface to be treated.

The cleaning agent is then dispersed in the volume, at a relative speed with respect to the biofilm or the high organic deposits and a surface action only. Thus, it does not penetrate over the entire thickness of the biofilm or of the inorganic deposit to be treated, a large part of the volume of cleaning agent injected at the inlet is found at the outlet, which requires large volumes of cleaning agents for reduced effectiveness. .

Other solutions to combat fouling, scaling or clogging by biofilms or inorganic deposits consist of stopping the fluid transport devices and disassembly for maintenance, said maintenance usually consisting of injecting a high fluid pressure or mechanical action so as to take off the films in question. This maintenance therefore requires the complete shutdown of the system periodically.

The object of the present invention is to provide a solution to fouling of heat exchanger systems and more generally of surfaces, by biological or inert structures.

General description of the invention

With this objective in mind, the present invention proposes the use of a polymer protective film applied to a surface of a wall in order to combat fouling / scaling, the protective film being dense (therefore generally considered to be non-porous / waterproof, in particular to liquids), but having permeability to a gaseous cleaning agent. Such a film therefore makes it possible to operate, through the protective polymer film, the supply of gaseous cleaning agent to the film / deposit surface interface.

According to a first aspect, the invention relates to a heat exchanger system comprising a wall separating a first fluid from a second fluid and allowing heat exchange between said fluids. The system is remarkable in that a protective film of polymer material is applied to said wall at least on the side of the first fluid, the protective film having a front face in contact with the first fluid and an opposite rear face, facing the wall exchange; in that gas distribution means are provided for distributing a gaseous cleaning agent on the side of the rear face of the protective film, and in that the protective film is a dense polymer film, in particular tight or not very permeable to the first fluid, any by presenting a permeability to said gaseous cleaning agent, so as to allow the gaseous cleaning agent to pass through the protective film towards the front face thereof.

It will be noted that the passage of the cleaning gas through the protective film takes place under the effect of the partial pressure difference between the rear face and the front face of the protective film. The cleaning action is therefore not based on the pressure force of the gaseous cleaning agent, but on its chemical action (e.g. oxidation or dissolution) with deposits on the front of the protective film.

Among the advantages brought by the invention one can note:

- high efficiency: the gaseous cleaning agent is brought directly and completely to the base of the deposit. The consumption of gaseous cleaning agent can thus be minimized, which is favorable from an economic and environmental point of view.

- rapid action: the intake induces a strong concentration gradient at the interface between the support and the deposit;

- flexibility of implementation: it is possible to modulate the frequency and duration of treatment in order to limit the thicknesses of the deposits / biofilms. In addition, the introduction of the gaseous cleaning agent through the protective film is independent of the presence or absence of liquid on the external surface; therefore there is no need to stop the heat exchange process for cleaning.

In a variant, a heat exchanger comprises at least one exchanger tube for the circulation of one of the two fluids, in heat exchange with the other fluid around the exchanger tube, said wall being constituted by at least a portion of said exchanger tube. The protective film is applied to the interior or exterior surface of the exchanger tube on the side of the first fluid, and optionally another protective film is applied to the surface of the exchanger tube on the side of the second fluid.

According to a second aspect, the invention relates to an article with an anti-deposit wall, said article comprising a wall having a surface covered at least in part by a protective film of polymer material having a rear face turned towards the wall and an opposite front face. . It will be appreciated that the protective film is a dense polymer film having permeability to a gaseous cleaning agent. Gas distribution means are provided for distributing the gaseous cleaning agent on the side of the rear face, and thus allowing the cleaning of the front face of the protective film when the gaseous cleaning agent passes through the protective film from the rear face towards the front face.

The combination of the protective film with a support wall covered by the protective film therefore forms an anti-deposit wall structure which can be used in a number of applications. An article is thus obtained, the wall of which can be cleaned.

Such an anti-deposit wall structure can of course be used in the field of exchangers, in particular heat but also material, tubular, planar or other.

However, the invention finds application in a variety of fields, in which a wall / surface is liable to be contaminated or to become fouled.

Thus in a variant the article is a tube or a pipe comprising a wall defining a passage for a liquid, and the protective film is applied to the internal and / or external surface of the wall. In particular, the protective film is applied over the entire interior or exterior periphery.

In addition to the applications of heat exchangers, a particularly interesting application of the invention is that of the simple transport of fluid. In this case the article is generally a tube, a pipe or a pipe and the protective film is applied to the internal surface of the wall. We are targeting here in particular a use in water network systems, in particular ultra-pure water used in certain industries.

But the article could also include a substantially planar wall, the protective film covering at least partially the surface of the planar wall. For example, the flat wall may be a table or bench, for example, in an analysis laboratory.

According to a last aspect, the invention relates generally to an anti-deposit wall system, in which the protective film permeable to the gaseous cleaning agent covers a massive wall, gas distribution means being provided for distributing a gaseous cleaning agent. on the back side of the protective film.

The technical characteristics mentioned below are generally applicable to the various aspects of the invention.

In the context of the invention, the protective film of polymer material is said to be “dense”, that is to say it is generally considered to be non-porous or waterproof, or at the very least not very permeable to liquids. However, the dense polymer film has permeability to gaseous cleaning agents.

Dense polymer materials combining mechanical, thermal and chemical resistance will therefore advantageously be chosen for the protective film, while being permeable to the gases used as cleaning agents.

In the context of the invention, it is considered that the protective film has a “selective” permeability to gaseous cleaning agents, in the sense that the polymer of the protective film is chosen for its affinity with predetermined gaseous cleaning agents, so as to present good permeability to these gaseous cleaning agents but not to other fluids liable to come into contact with the wall during use.

The permeability of a polymer makes it possible to evaluate the quantity of material passing through a material of given thickness per unit of surface and time, for a normalized driving force. The most frequently used unit is the Barrer (1 Barrer = 10 ^'10 cm ³ sTpcm' ² .cm.s' ¹ .cmHg · ¹ ). The permeability of polymeric materials vis-à-vis different gaseous or liquid compounds is referenced for many systems and can be determined experimentally by standardized techniques (time lag method for example).

Depending on the applications, the polymer will therefore be chosen for the protective film so that it has good permeability to the cleaning gas, for example of the order of 1 to 1000 bars, preferably between 100 and 1000 bars, while being substantially impermeable, or not very permeable to the fluid in contact with the wall. The permeability to cleaning gas of the protective film may in particular be of the order of 500 Barrer. In addition, the protective film preferably has a permeability to the fluid in contact with the wall of less than 100 bars. It will be noted in this context that the passage of the fluid in contact with the protective film can be greatly limited by fixing a partial pressure downstream, on the rear face side (for example the use of a wet gaseous cleaning agent, in order to block the passage of water).

For example, the protective film can be made of PolyTetraFluoroEthylene, PolyMethylPentene, PolyEtherSulfone, Polysulfone, Ethylene-Propylene-Diene (EPDM), Polyimide, Cellulose acetate, Ethylcellulose, Polydimethylsiloxane, Polyamide, or PolyEtherBlocAmide.

For cleaning conventional deposits of biofilms, tartar, etc., the gaseous cleaning agent is chosen from the following agents: CO2, CI2, O3, H2O2, pure or diluted, and their mixtures.

The above-mentioned polymers have the desired selectivity and permeability with respect to these gaseous cleaning agents, while offering limited permeability to liquids such as water or the fluids used in the exchangers.

The gas distribution means can take any suitable form to supply the gas to the rear of the protective film, depending on the applications and embodiment. As the gas flow takes place due to the partial pressure difference of the cleaning gas (low concentration at the front), there is no need for high pressures in the distribution means, respectively behind the protective film .

The gas distribution means are advantageously designed to distribute the cleaning gas substantially over the whole of the rear face of the protective film, to allow a uniform / homogeneous treatment.

According to the variants, the gas distribution means comprise a network of channels for the distribution of gas. These channels can be formed directly in the wall, therefore located under the protective film. Here it is possible to use any technique for structuring the surface of the support wall (plate or tube), and in particular: stamped grooves, machined or extruded, chemical etching, abrasion; these surface preparations should allow the homogeneous distribution of the active agent (free circulation of the cleaning gas).

Alternatively, the channels can be provided in an intermediate layer, between the wall and the protective film. This involves placing a porous interlayer such as a textile film, polymer foam or metal, perforated metal, allowing the creation of a space between the protective film and the wall, capable of conveying the cleaning gas.

Preferably, the gas distribution means comprise an inlet manifold in communication with said network of channels. They can also include an outlet manifold, to allow a purge, e.g. by circulating a purge gas between the inlet and outlet manifold.

The fixing of the protective film to the wall which supports it can be done by any suitable means, in particular by gluing or by mechanical means (eg crimping), at the periphery of the plate. Alternatively, the protective film may have adhesion properties, in particular during its implementation.

In some variants, the protective film and the wall (exchanger or pipe) can be made of the same material, preferably with the cleaning gas distribution network. In this case we can manufacture the whole in one piece, for example by extrusion or 3D printing.

Depending on the applications, depending on the polymer of the protective film and the fluid flowing along the protective wall, and the conditions of use, a fraction of the fluid can diffuse through the wall on the side of the rear face. We can then find in the distribution means (grooves and others) a condensate (in particular condensed water vapor). It will be noted here that the distribution means form a dead end for the gas, which is not conducive to the flow of the fluid coming from the front face by permeance, despite a low permeance. This condensate can be drained, for example.

The fields of application of the invention are vast: heat exchangers (domestic, medical or industrial use), laboratory equipment with a strong constraint on the formation of biofilms (medical, microbiological analysis laboratories), supply pipes for drinking water, or ultra pure water (pharmaceutical industry, electronic components) contactors with dense skin membranes, reverse osmosis units, transmembrane distillation, direct osmosis type processes for energy production (PRO), pharmaceutical laboratories drug production; Highly sensitive medical sectors (fight against the formation of biofilms on bench tops for example), cooling towers ...

Detailed description using the figures

Other features and characteristics of the invention will emerge from the detailed description of at least one advantageous embodiment presented below, by way of illustration, with reference to the accompanying drawings. These show:

Fig.1: a diagram illustrating the principle of the invention with a) configuration of conventional heat exchanger, b) cleaning operation of the conventional exchanger and c) heat exchanger implementing the invention;

Fig. 2: diagram of a pipe comprising a protective film on its outer surface;

Fig. 3: diagram of a pipe comprising a protective film on its interior and exterior surfaces;

Fig.4: an embodiment of a heat exchanger plate;

Fig. 5: block diagram of a work plan with a protective film; and

Fig. 6:. Schematic diagram of a pipe including a protective film on its inner surface.

The principle of the invention will first be explained with reference to FIG. 1. FIG. 1a shows diagrammatically a principle of a conventional heat exchanger, in which a transfer of heat between two fluids, materialized respectively by arrows 2 and 4, takes place through a wall 6 (heat exchange wall), without mixing between the fluids. The wall 6 is generally made of a solid polymer, non-porous and having appropriate mechanical and chemical resistance. Over time, the exchange surface of the wall 6 becomes dirty: a deposit 8 of biofilm is formed on the side of the fluid 4.

The fight against fouling of the surface is conventionally done by adding a cleaning agent, also called active agent, (for example chlorine) in the fluid 4 to come into contact with the deposit on the liquid vein side, as shown schematically in Fig. 1 b).

Finally, the principle of the invention is illustrated in Figure 1c). We recognize the wall 6 (solid and non-porous) which separates the two fluids and allows heat transfer between them without direct contact. As above, the wall 6 comprises two opposite faces 6.1 and 6.2 which constitute heat exchange surfaces. It will be noted that the reference sign 10 designates a protective film of polymer material which covers at least in part the surface 6.1 of the wall 6 on the side of the fluid 4. The polymer film 10 has a front face 10.1 in contact, in use, with the fluid 4 and an opposite rear face 10.2, facing the wall 6. The protective film 10 is dense, therefore impermeable to the fluid 4, while being permeable to a gaseous cleaning agent (represented by the horizontal arrows), which can be introduced on the side of the rear face of the protective film 10 so as to pass through the protective film and attack the deposit 8 at “countercurrent”. The distribution of the gaseous cleaning agent at the rear of the protective film 10 is done by means of gas distribution explained below.

The present concept therefore proposes the supply of active gaseous cleaning agent (for example CO2, CI2, O3, H2O2 ...) through a dense polymer film having a predetermined and selective permeability for the gaseous cleaning agent, allowing a cleaning action at the surface / depot interface.

We therefore propose here an anti-deposit wall principle which makes it possible to set up strategies for combating fouling, scaling or clogging by biofilm of the surfaces of the exchangers, or more generally of walls, by applying, in a manner intermittent, a flow of suitable cleaning gas compounds in the opposite direction to deposition. Indeed, the means of control conventionally used to prevent deposits of tartar or biofilms (the most frequent cases encountered in industrial practice) are based on pretreatments of the fluids to be treated (addition of sequestering agents or biocides for example), or to sequences for cleaning surfaces by circulating active solutions (“Cleaning In Place”, CIP, and “Disinfection In Place”, DIP procedures: acids, bases, biocides, etc.). The use of a gaseous attack agent for the deposit by a countercurrent supply, via the wall material of the exchanger, has the following advantages:

- Greater efficiency, insofar as the agent is fully brought into direct contact at the base of the depot.

- A faster action, which can lead to a lower consumption of the agent used, insofar as the intake induces a strong concentration gradient at the interface between the support and the deposit. This singularity is capable of rapidly causing a dropout of the deposit, by breaking the contact points between the deposit and the material (for example dissolution of calcium carbonate by adding CO ₂ or attack on biofilms by adding oxidants from type Cl or O3).

- A limitation of the thicknesses of the deposits / biofilms by modulating the frequency and the duration of the preventive treatments without generating stops penalizing heat exchangers.

In general, the supply of cleaning gas is done selectively, that is to say intermittently, by adjusting the frequency and duration of gas supply according to the desired treatment. It is however possible to make a continuous contribution.

The protective film is a dense polymer film, that is to say it is generally considered to be non-porous or waterproof, and is in particular impermeable to liquids. However, the dense polymer film has permeability to gaseous cleaning agents, in particular to CO ₂ , Cl ₂ , O3, H ₂ O ₂ .

As an example, polymers such as PolyTetraFluoroEthylene, PolyMethylPentene, PolyEtherSulfone, Polysulfone, Ethylene-Propylene-Diene (EPDM), Polyimide, Cellulose acetate, Ethylcellulose, Polydimethylsiloxane, Polyamide may be used for the protective film.

PolyEtherBlocAmide, or Teflon-AF. These polymers are particularly interesting because they are dense and combine mechanical, thermal, and chemical resistance, while being permeable to gases but impermeable to liquids (or low permeability). These examples are not limiting and a person skilled in the art can use other polymers meeting these criteria.

The gas permeance of the protective film can be adjusted by varying the thickness and the choice of polymer. This allows certain adaptations to the choice of cleaning gas. In general, the protective film can have a thickness of the order of 0.1 μm to 2 mm, more particularly from 0.5 to 10 μm.

Different approaches can be adopted for the arrangement of the protective film against the exchanger wall (support wall) which supports the protective film.

According to one embodiment, the protective film and the wall can be made of the same material, for example by extrusion. This allows in particular to make grooves in the support wall for the distribution of the cleaning gas. This solution avoids the difficulties that could be encountered with a composite material. A protective film with a wall thickness of the order of a millimeter, with a material permeable to one of the active agents targeted, is compatible with extrusion, the support wall having a greater thickness in order to constitute a tight, solid wall.

Alternatively, depending on the choice of polymer, this may have, during its deposition or its implementation, a certain sufficient adhesion for its fixing against the support wall. In addition, the protective film is fixed with an adhesive.

It will also be noted that, since no overpressure of the active gaseous agent relative to the biofilm generating fluid is necessary, there is no risk of deformation or degradation of the geometry of the system by the pressure of the 'gaseous agent. It is therefore possible to apply the protective film without seeking complete adhesion of the surface.

In this context also, it is possible to envisage the mechanical retention of the polymeric protective film at its periphery, exerting sufficient pressure along a peripheral line of the protective film in order to avoid the escape of the gaseous agent.

In the case of a plate-shaped protective film, peripheral crimping can be carried out. In the case of pipes / conduits, it is possible to use a protective film in the form of a tubular sheath, with sealing at the level of flat flanges by means of flanges produced at the ends of the sheath.

In summary, the polymer film can be maintained at least at its ends and at least to ensure the tightness of the device allowing a homogeneous supply of the active agent between the latter and the support (plate, tube).

An alternative embodiment of a tube 20 provided with a protective film according to the invention is illustrated in FIG. 2. The tube 20 comprises a cylindrical wall 22 having an internal surface 22.1 and an external surface 22.2 and defining an internal passage 24. The tube 20 can be made of any suitable material, metallic or polymer, depending on the application envisaged.

For use as a heat exchanger, the wall 22 constitutes a heat exchange wall between a first fluid, circulating in the internal passage 24 and a second fluid, on the opposite side of the wall 22.

The external surface 22.2 of the tube is covered, over its entire periphery, with a dense protective film 26 of polymer material as explained with reference to FIG. 1. The protective film 26 is impermeable to the second fluid which circulates outside of the tube 20. As indicated above, the protective film 26 can be produced such as a tubular sheath having a diameter corresponding to the external diameter of the tube 20 and held in place by its ends.

The protective film 26 is chosen to have selective permeability to one or more gaseous cleaning agents while being impermeable (or less permeable) to the second fluid (in particular liquid) circulating outside the tube 20 and in contact with the external face of the protective film 26. The cleaning gas is supplied to the rear of the protective film 26 by a series of grooves 28 (longitudinal grooves parallel to the axis of the tube) produced in the external surface of the tube. By introducing the cleaning gas into these grooves 28, it can be distributed over the entire length of the tube 20.

As the protective film 26 is permeable towards the cleaning gas, it will be able to pass from the rear face 26.1 of the film 26 to the front face 26.2, and therefore meet the base of the deposits (biofilms or others) which have tendency to form. The protective film 26 being however impermeable, in particular to the second fluid in contact with the protective film, the second fluid does not penetrate into the grooves 28.

It will also be noted with interest that the passage of the cleaning gas through the film 26 takes place mainly due to the difference in partial pressure of the cleaning gas between the two faces of the protective film 26. It is therefore not necessary to maintain a significant gas pressure in the spline network. Thus, the cleaning of the deposits on the surface 26.2 is done because of the chemical activity of the chosen cleaning agent, and therefore not because of the use of gas pressures aimed at removing the deposits.

Another embodiment is illustrated in FIG. 3, in which the tube 20 of FIG. 2 is provided with a protective film 26 on the internal and external surface. The tube 20 therefore includes grooves 28 'in the inner periphery of the wall, that is to say in the inner surface 22.2.

In the variants of FIGS. 2 and 3, the wall 22 of the tube 20 acts as a structural and heat exchange wall, as well as as a protective film support. In addition, the grooves 28 and 28 ’, which form a gas distribution means or network, are formed directly in the wall 22 of the tube. Such grooves or grooves for the distribution of gas are obviously easily produced by extrusion conventionally used for the manufacture of tubes, or even by machining or 3D printing.

Alternatively, as indicated above, an intermediate layer can be formed on the exchange surface to be protected, this intermediate layer being capable of supporting the protective film and comprising a network of open cells or channels, of random or deterministic distribution, capable distributing the cleaning gas in a substantially uniform manner over the entire rear surface of the protective film. One could for example form an intermediate layer of polymer or metallic foam with open porosity.

FIG. 4 schematically illustrates a plate 30 for a plate heat exchanger according to a variant of the invention. Conventionally, the plate 30 has a generally rectangular shape and includes orifices 32 for the passage of conduits (not shown) for the introduction or collection of fluid. The plate 30 forms a partition wall between two fluids and therefore comprises a front face 30.1 and an opposite rear face, which form exchange surfaces.

In order to allow the exchange surface to be clogged, the front face 30.1 is partially covered by a protective film 34 (shown in dotted lines) which covers the majority of its surface. The protective film 34 is of the same type as the protective film described above, that is to say that it is impermeable to the fluid / liquid which will, in use, come into contact with the protective film and that it has permeability to a gaseous cleaning agent supplied by the rear face of the film 34, that facing the front face 30.1 of the plate 30. The protective film 34 is fixed to the plate at its periphery by bonding or by any suitable means, eg. crimping (not shown).

The cleaning gas distribution means comprise a plurality of longitudinal grooves 36 produced in the front face 30.1 and forming a cleaning gas distribution network. The cleaning gas is introduced into the grooves 36 through a transverse groove 38 forming an inlet manifold, communicating with an inlet port 40 via a pipe 42. As for the variants of FIGS. 2 and 3, the grooves 36, 38 are closed , in the plane of the surface 30.1 of the plate, by the protective film 34. The cleaning gas is therefore in contact with the rear face of the film 34 and diffuses towards the front face of the latter under the effect of the difference partial pressure of the cleaning gas between the two faces.

A gas source 44 comprising a pipe 46 with an adjustment valve 48 is connected to the inlet port 40. The valve 48 allows the selective introduction of predetermined quantities of gas into the network of grooves 38.

It will also be noted that in the above variants which employ grooves or grooves for the distribution of cleaning gas, the protective film comes to close them in a sealed manner to the circulating exchanger fluid. Thus, the cleaning gas is directly in contact with the rear face of the protective film, but the fluid / liquid on the side of the front face cannot penetrate into the distribution channels of the cleaning gas.

A final variant relating to a work surface 50 with an anti-deposit wall is schematically represented in FIG. 5. There is recognized a table with four legs 52 and a tray 54 defining a work plane. The upper surface of the work surface is completely covered by a protective film 56 of dense polymer, generally liquid-tight and having permeability to a gaseous cleaning agent. Between the two is an intermediate layer 58 forming a gas distribution network. It is for example a rigid polymer foam with open pores or a polymeric woven (sieve type). The reference sign 60 designates an inlet manifold (shown in dotted lines) which extends over the entire width of the intermediate layer 58 and over its thickness. It has a box shape connected on one side to a source of cleaning gas 62 and open on the intermediate layer 58. It allows the introduction of the cleaning gas into the intermediate layer. As the porosity of the intermediate layer 58 is open, the gas circulates therein and comes into contact with the rear face of the protective film 28. The four lateral sides of the intermediate layer 58 are closed in leaktight manner by any appropriate means, for example heat-sealed strips. The reference sign 61 designates a gas supply pipe fitted with a tap, which allows the selective introduction of cleaning gas into the intermediate layer. Preferably the supply pipe 61 ends with a fitting which cooperates with a fitting of the inlet manifold 60, which makes it possible to separate the two fittings and therefore to disconnect the gas source, which is only required when the '' we want to operate a cleaning of the work surface.

Opposite the inlet manifold is optionally an outlet manifold 64 similar to the inlet manifold 60. A tap (not shown) is associated with the outlet manifold and makes it possible, if necessary, to make the intermediate layer communicate with outside, for example in the event of a purge. This valve is generally closed so that all of the gas introduced via the inlet manifold 60 flows towards the front face of the protective film.

Finally, Figure 6 relates to an application of the invention to water network systems. Here the reference sign 20 ”designates a pipe whose wall 22 carries on its internal face 22.1 the protective film 26. As in the variant of FIG. 3, grooves 28 ′ allow the distribution of the gaseous cleaning agent to the the rear of the protective film 26. The fluid flowing in the internal passage 24 of the pipe 20 ”is therefore in contact with the protective film 26 and its surface can be kept clean by injection of the gaseous cleaning agent. Such a pipe provided with an anti-deposit wall can be used for the supply of water in general, and finds a particularly advantageous application for the supply of ultra-clean water.

Claims (19)

claims 1. A heat exchanger system comprising a wall (22) separating a first fluid from a second fluid and allowing heat exchange between said fluids; characterized in that a protective film (26) of polymeric material is disposed on said wall at least on the side of the first fluid, the protective film having a front face (26.2) in contact with the first fluid and a rear face (26.1) opposite, facing the wall (22); in that gas distribution means (28) are provided for distributing a gaseous cleaning agent on the side of the rear face (26.1) of the protective film; and in that the protective film (26) is dense, impermeable or not very permeable to the first fluid, while being permeable to said gaseous cleaning agent, so as to allow the gaseous cleaning agent to pass through the protective film towards the front face ( 26.2) of it. 2. System according to claim 1, in which the gaseous cleaning agent diffuses towards the front face (26.2) of the polymer film (26) under the effect of the partial pressure difference between the two faces. 3. System according to claim 1 or 2, wherein the gaseous cleaning agent is chosen from among the following gases: CO2, CI2, O3, H2O2, pure or diluted, or their mixtures. 4. The system of claim 1, 2 or 3, wherein the dense protective film has a permeability to gaseous cleaner between 1 and 1000 Barrer, preferably between 100 and 1000 Barrer. 5. System according to any one of the preceding claims, in which the dense protective film has a permeability to gases and liquids in contact with its front face which is less than 100 bars. 6. System according to any one of the preceding claims, in which the protective film is made of PolyTetraFluoroEthylene, PolyMethylPentene, PolyEtherSulfone, Polysulfone, Ethylene-PropyleneDiene (EPDM), Polyimide, Cellulose acetate, Ethylcellulose, Polydimethylsiloxane, Polyamide, PolyEtherBlocAmide, ouTeflon-AF. 7. System according to any one of the preceding claims, comprising at least one exchanger tube (20) for the circulation of one of the two fluids, in heat exchange with the other fluid around the exchanger tube, said wall (22) being constituted by at least a portion of said exchanger tube, and in which said protective film is applied to the inner or outer surface of the exchanger tube on the side of the first fluid, and optionally another protective film is applied to the surface of the exchanger tube on the side of the second fluid. 8. The system of claim 7, wherein the protective film is made such as a tubular sheath along the inner surface, respectively outer. 9. System according to any one of the preceding claims, in which the gas distribution means are designed to distribute the gaseous cleaning agent over substantially the whole of the rear face of the protective film. 10. The system of claim 9, wherein the gas distribution means comprise a network of channels for the distribution of the gaseous cleaning agent. 11. The system of claim 10, wherein the channels are formed by grooves (28, 28 ’) formed in the wall under the protective film. 12. The system of claim 10, wherein the channels are provided in an intermediate layer, between the wall and the protective film, the intermediate layer preferably comprising a textile film, a polymer or metal foam, perforated metal, or a combination. of these. 13. The system of claim 9, 10 or 11, wherein the protective film and the gas distribution means are manufactured in one piece with the wall. 14. System according to any one of the preceding claims, in which the gas distribution means comprise an inlet manifold in communication with said network of channels. 15. The system of claim 14, wherein the gas distribution means comprise an outlet manifold, in order to allow a purge by circulating a purge gas between the inlet and outlet manifold. 16. Article with anti-deposit wall, said article comprising a wall (22, 30, 54) having a surface covered at least in part by a protective film (26, 34, 56) of polymer material having a rear face facing the wall and an opposite front face, characterized in that said protective film is a dense polymer film having selective permeability to a gaseous cleaning agent, and in that gas distribution means (28, 28 ', 36, 58) are intended to distribute the gaseous cleaning agent on the side of the rear face, and thus allow the cleaning of the front face of the protective film when the gaseous cleaning agent passes through the protective film from the rear face to the front face. 17. Article according to claim 16, in which said article is a tube, a pipe (20, 20 ') or a water pipe (20 ”) comprising a tubular wall (22) defining a passage for a liquid, and that the protective film (16) is applied to the internal and / or external surface of the wall. 18. The article of claim 16 wherein said article (30, 50) comprises a substantially planar wall, said protective film covering at least in part the surface of the planar wall. 19. The article of claim 18, wherein said article is a wall of a worktop.